, and made it virtually unknown just a week later. and the entirety ofthelawenforcementthat worked this case should be commended for their efforts. >> reporter: court documents also contain new details about thursday night's carjacking. the fbi says surveillance pictures show dzhokhar and tamerlan tsarnaev at a gas station in cambridge where they drove with the owner of the suv they carjacked. one of them, investigators say, began the carjacking by pointing a gun at the driver and saying, "did you hear about the boston explosion? i did that." the carjacker showed the driver that he had bullets in his gun according to the fbi and said, "i'm serious." at the scene of the shootout in watertown where tamerlan tsarnaev was killed, other explosive devices were also found. in an interview for "dateline" nbc, the boston police commissioner says that's one reason he thinks the brothers planned other attacks. >> we had to step over some unexploded devices that they threw at the officers. and i can only understand from that that they had other targets. they were going other places. >> that wa